Field of the Invention
The present invention relates to an on-vehicle communication system that performs message authentication.
Description of the Background Art
To date, an on-vehicle communication system that uses encryption key to perform message authentication has been known. This type of on-vehicle communication system is described in Japanese Laid-Open Patent Publication No. 2013-098719 (hereinafter, referred to as Patent Literature 1). In the on-vehicle communication system described in Patent Literature 1, after a main message including data to be communicated has been transmitted, an MAC message including an MAC (message authentication code) for a data filed of the main message is transmitted. The MAC is obtained by an AES encryption algorithm that is one of common key block encryption methods. The validity of the main message is verified on a receiver side by determining whether or not the MAC obtained from the data filed of the received main message matches the MAC included in the received MAC message.
Further, an on-vehicle communication system that is connected to a network outside the vehicle, has been known. As this type of on-vehicle communication system, a system that performs wireless communication with an external device via a data communication module (DCM) is put into practical use.